The invention relates to motorcycles, and more particularly to motorcycles having overhead cam engines.
The use of overhead cam engines, and more particularly dual overhead cam engines, is well known in the motorcycle industry. Tolerance limits on the casting process used to form the cylinder head of an overhead cam engine make it necessary to ream the cam shaft bearing seats, which are integrally cast into the cylinder head. The reaming ensures the proper alignment and rotation of the camshafts inside the cam case. In order to ream the bearing seats in the relatively confined cylinder head casting, it is necessary to first cast or machine a semi-circular recess in the side wall of the cylinder head and in alignment with the bearing seats. The reaming bit then has an unobstructed path to perform its operation. Aside from facilitating the reaming operation, the semi-circular recess in the cylinder head serves no purpose and must be closed off when the cam cover is placed on the cylinder head.
Prior art dual overhead cam engines typically include a resilient sealing gasket at the split line between the cylinder head and the cam cover. The sealing gasket includes integral semi-circular or xe2x80x9chalf-moonxe2x80x9d cam end cover portions that fit in the semi-circular recesses so that the cylinder head and the sealing gasket together form a substantially flat and continuous upper peripheral edge. The cam cover, which has a flat lower peripheral edge corresponding in shape to the upper peripheral edge of the sealing gasket, is then mounted on the cylinder head to enclose the cam shafts and define the upper portion of the cam case. The sealing gasket substantially seals the joint between the cylinder head and the cam cover.
Prior art cam case sealing gaskets suffer from various problems. The half-moon cam cover portions are typically molded from the same resilient, elastomeric material as the remainder of the sealing gasket. Because of their resilience, the cam end cover portions often provide a less than adequate seal between the cylinder head and the cam cover. Typically, silicone or other sealing materials must be used on the cam end cover portions, the cam cover, or both prior to mounting the cam cover on the cylinder head to ensure that the semi-circular recesses remain properly sealed. The sealing material may also need to be re-applied each time the cam cover is removed and then re-assembled. The elastomeric half-moon cam cover portions also tend to lack aesthetic appeal.
The present invention provides a motorcycle including a frame, an engine crankcase and cylinder assembly coupled to the frame, a cylinder head coupled to the crankcase and cylinder assembly, a cam cover coupled to the cylinder head, and a substantially rigid insert. The cylinder head includes a camshaft support surface and a cylinder head wall. The camshaft support surface defines a camshaft axis and the cylinder head wall partially defines an aperture that is substantially axially aligned with the camshaft axis. The cam cover cooperates with the cylinder head wall to further define the aperture, and the insert is positioned in the aperture.
The aperture includes a first boundary that is defined by the cylinder head, and a second boundary that is defined by the cam cover, and the insert includes a first profile corresponding to the first boundary, and a second profile corresponding to the second boundary. In some embodiments, the first and second profiles cooperate to define a semi-circular inner portion of the insert. In other embodiments, the first and second profiles cooperate to define a circular inner portion of the insert.
The motorcycle may also include a sealing jacket that surrounds the insert and engages the cylinder head and the cam cover. The sealing jacket may be integrally formed with a resilient sealing member that is positioned between the cylinder head and the cam cover. The insert may also include a substantially circular outer portion that overlies portions of the cylinder head wall and the cam cover.
The present invention also provides a method for sealing an interface between a cylinder head and a cam cover. The cylinder head includes a camshaft support surface that defines a camshaft axis, and a cylinder head wall that defines an aperture. The aperture is adjacent the interface and is substantially aligned with the camshaft axis. A substantially rigid insert is provided and a resilient sealing member including a resilient sealing jacket is positioned around the insert. The resilient sealing member is located between the cylinder head and the cam cover such that the resilient sealing jacket and the insert occupy the aperture.
The present invention also provides a method of making a sealing gasket and insert assembly for an overhead cam motorcycle engine. The method includes providing a rigid insert and a continuous sealing gasket that includes a sealing jacket defining an opening. The sealing gasket is positioned around the insert such that the insert is positioned in the opening and the sealing jacket substantially surrounds and retains the insert. The gasket may be molded around the insert or alternatively the insert may be pressed into the opening.
The present invention also provides a method for replacing a substantially rigid old insert having an inner portion received by an opening in a sealing gasket. The sealing gasket is positioned in an interface between a cylinder head and a cam cover of an overhead cam motorcycle engine, and the old insert has an outer portion overlying portions of the cylinder head and the cam cover. The method includes providing a substantially rigid replacement insert including an inner portion that is positionable within the opening. The old insert is removed from the opening; and the replacement insert is inserted into the opening. A replacement sealing gasket including an opening may also be provided and the replacement sealing gasket may be positioned in the interface in place of the original gasket.
The present invention also provides a method for replacing a sealing gasket positioned in an interface between a cylinder head and a cam cover of an overhead cam motorcycle engine. The sealing gasket includes an opening that receives an inner portion of a substantially rigid insert, and the insert has an outer portion overlying portions of the cylinder head and the cam cover. The method includes decoupling the cam cover from the cylinder head and removing the sealing gasket from the interface. The insert is removed from the sealing gasket opening and a replacement sealing gasket including an opening configured to receive the inner portion of the insert is provided. The inner portion of the insert is inserted into the opening of the replacement gasket, the replacement gasket is positioned in the interface, and the cam cover is recoupled to the cylinder head.
Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims, and drawings.